Introduction  |  Measurement  |  Modules  |  Demosaicing Purple fringing – CA correction for non-tangential edges Introduction Chromatic aberration (CA) is one of several aberrations that degrade lens performance. (Others include coma, astigmatism, spherical aberration, and curvature of field.) It occurs because the index of refraction of glass varies with the wavelength of light, i.e., glass bends different colors by different amounts. This phenomenon is called dispersion. It appears as color fringing, most visibly on tangential edges near the boundaries of the image. It is sometimes confused with another effect, which we call pixel shift— a color channel offset that is […]

Imatest 5.2 has several new features that let you use measured chart modulation transfer function (MTF) to do the following: Determine the suitability of a test chart characterized by size (height), print media, and printing technology for camera MTF measurements where the camera is characterized by pixel size, which is typically the number of vertical pixels. This can help determine the appropriate test chart for a specific application. This capability has been enhanced in Imatest 5.2  with the addition of the Chart suitability display. Increase the accuracy of MTF measurements by dividing the measured camera MTF by the appropriately scaled chart […]

Imatest 5.1 has important new capabilities for measuring and correcting MTF degradation caused by test charts. These new capabilities are far easier to understand and apply than CQI. Chart quality calculator Compensating camera MTF measurements for chart and sensor MTF As a result of the improved measurements, the Chart Quality Index measurement has been deprecated. The Chart Finder is an interactive web page that can help you select the appropriate chart size and media. It contains results from this page, but without the math. Summary In order to determine the suitability of a test chart is for measuring the performance of a […]

Postprocessor for viewing summaries of SFR, SFRplus results Introduction to Batchview Batchview is a postprocessor for displaying lens test results generated by SFR, SFRplus, and eSFR ISO batch runs (analyses of groups of test chart images taken at various apertures, focal lengths, etc.). It can store and display up to four sets of results for convenient comparisons in Imatest Master; two in Studio. Postprocessor comparison Each lets you compare sharpness of different regions and/or images MTF Compare Postprocessor to SFR, SFRplus, and eSFR ISO. Input is two CSV results files for individual regions. Lets you compare individual edges from any region […]

Imatest 4.4+ can evaluate auto-focus (AF) as a measure of MTF with respect to time. This can be performed by using the SFR module with an appropriate video file. Uses/Purpose This metric is intended to be used as a way to measure the time a camera system takes to auto-focus. Rise time and settling time are automatically calculated. This measurement does not provide information about the accuracy or precision of auto-focus. To evaluate those measures, several measurements should be performed on the final, settled images and compared. File Selection and Frame Selection Begin by clicking on SFR from the main window and select a […]

Analyses & Output – INI settings – Chart Definition Files – Chart Definition Utility   INI file fields relevant to Arbitrary Charts The following INI fields are currently exposed to the user to control the behavior of the Arbitrary Charts module and its output. They have been organized here by topic, but do not need to be in any particular order or grouping in your INI file itself.    [arbcharts] section Slanted-edge Analysis     Texture Analysis   Star Analysis   Wedge Analysis   Uniformity Grid Analysis   Color/Tone/Noise   Perceptual metrics   Module operation and misc.   [api] section   […]

Analyses & Output – INI settings – Chart Definition Files – Chart Definition Utility   Data outputs from the Arbitrary Charts Module are different from other modules in Imatest: Only JSON files are output, not CSV or XML. The structure of JSON is substantially different than other modules.  If several images are run in a batch, results from all images may be contained in a single JSON. Since the Arbitrary Charts Module is based on the concept of a custom layout of features, there is no fixed structure to the measurement results that the Module produces. Instead, the module simply produces […]

Analyses & Output – INI settings – Chart Definition Files – Chart Definition Utility   Combine all the features you need to analyze into a single chart Introduction The Imatest™ Arbitrary Charts module analyzes images of custom test charts. A chart-definition file (typically user defined) is needed to describe the chart layout to Imatest software. The Arbitrary Charts module will automatically locate and analyze target features when an observed image of a chart is loaded along with the corresponding definition file.    This module allows users to get a number of measurements out of custom, legacy, or competitors’ charts which are unsupported […]

Introduction to Acutance and SQF   Acutance and Subjective Quality Factor (SQF) are measures of perceived print or display sharpness. SQF was used for years in the photographic industry but has remained unfamiliar to most photographers. Acutance is a relatively new measurement from the IEEE Camera Phone Image Quality (CPIQ) group. Both are metrics which incorporate the effects of The imaging system: The Modulation Transfer Function (MTF) of the camera as a measurement of its intrinsic sharpness. The viewer: The human eye’s sensitivity to each spatial frequency modeled with a Contrast Sensitivity Function (CSF). The viewing conditions: The image display height […]

The Pass/Fail monitor (introduced In Imatest 4.0) provides a real-time indication of whether a device has passed or failed a test. It saves the trouble of digging through results— in figures or CSV or JSON files. Key features: It can stay open while modules run, displaying results immediately after calculations are complete. It works best on systems with a high resolution screen or dual screens. It interfaces with most Imatest analysis modules. It can be extremely valuable for developing and testing Pass/Fail criteria for Imatest IT (Industrial Testing). It can call several utilities for helping with this process. It displays […]

Introduction Part 1 of this page illustrates images analyzed in Random Scale-invariant & Dead Leaves. The images are not shown original size; they’ve been resized to be approximately equal in magnification with respect to the original chart image— with enough magnification to show the results of the camera optics and image processing. Part 2 demonstrates how demosaicing is the cause of a commonly observed discrepancy between Spilled Coins and slanted-edge MTF measurements. Part 1: Images used in Random / Dead Leaves Original pattern (cropped from the middle of the chart), for reference. Original pattern (reduced from file used to print […]

Introduction: Starting in version 4.5, Imatest is capable of performing the cross-correlation based texture blur measurement which is under consideration for ISO 19567-2: Texture Analysis on Stochastic Pattern. This is a texture-blur-analysis method originally proposed in Description of texture loss using the dead leaves target: Current issues and a new intrinsic approach by Kirk et al at Image Engineering.  This method starts from the same principles as the so-called “Direct” method of Cao et al which is the Power Spectral Density-based method described on the Random Module page. The main difference is the Direct method makes use of assumed statistical properties […]

Overview Starting in Imatest 4.4, it is possible to perform basic analysis of a video system’s ability to auto focus (AF), auto white balance (AWB) or auto expose an image (AE). Combined, these three tests may be referred to as AAA analysis. Currently, temporal analysis is only compatible with the following modules: Auto Focus: SFR Auto White Balance: Colorcheck Auto Exposure: Stepchart When you select one of these modules and read a video file, the fourth option in the Imatest Video Reader, plot metric with respect to time, will be made available. Selecting this option begins the appropriate setup for […]

Test Charts creates test chart files for printing on high quality inkjet printers. This page focuses on Scalable Vector Graphics (SVG) charts, many of which are used for measuring sharpness (MTF) with Imatest SFR, SFRplus, eSFR ISO, Checkerboard, and SFRreg. (Bitmap charts are described elsewhere.) SVG charts can be printed any size at a printer’s maximum quality (i.e., resolution) with no limitations, and they generally require much less storage than bitmap images. The SVG charts designed for automated testing with SFRplus and eSFR ISO (based on ISO 12233:2014/2017) have numerous advantages over the familiar but obsolete ISO 12233:2000 chart. Most […]

 Analyze the Siemens Star chart News:  Imatest 2020.1 (Feb. 2020)  Shannon information capacity can be calculated from images of the Siemens star, with much better accuracy than slanted-edges. The old slanted-edge method has been deprecated. The new feature will be available in the Pilot program prior to the release.  The white paper, “Camera information capacity: a key performance indicator for Machine Vision and Artificial Intelligence systems“, which briefly introduces information theory, describes the camera information capacity measurement, then shows results (including the effects of artifacts) is now available for download. Imatest 5.0: Half-stars (rotated by multiples of 45º) can now […]

A comparison of sensitivity to signal processing: Results for additional cameras This page contains additional Slanted-edge, Siemens Star, and Log F-Contrast results for four cameras, in support of claims in Slanted-edge versus Siemens Star that Siemens Star MTF measurements are nearly as sensitive to sharpening as low-contrast (4:1) slanted-edge measurements. The Siemens Star’s high contrast (specified at >50:1) makes it quite sensitive to saturation and to “shoulders” (regions of reduced contrast) in camera tonal response. Slanted-edge MTF measurements are stable, reliable, and more representative of perceived image sharpness under a wide range of conditions (in addition to their many well-known […]

A comparison of sensitivity to signal processing In this page we address concerns about the sensitivity of slanted-edge patterns to signal processing, especially sharpening, and we correct the misconception that sinusoidal patterns, such as the Siemens star, are insensitive to sharpening, and hence provide more robust and stable MTF measurements. The Siemens Star is of particular interest because, along with the slanted-edge, it is included in the ISO 12233:2014 standard.  To summarize our results, we found that sinusoidal patterns are sensitive to sharpening, though often less so than low contrast (4:1) slanted-edges. The relatively high contrast of the Siemens Star […]

Analysis of random scale-invariant patterns, including the Spilled Coins (Dead Leaves) Pattern, for measuring texture sharpness Introduction – Obtaining – Photographing – Running – Automatic ROI detection – Output  MTF – MTFnn, MTFnnP – Power Spectral Density – Equations & Scale-invariance   Introduction  Random/Dead Leaves, which runs under the interactive Rescharts interface or as a fixed (non-interactive, batch-capable) module, measures SFR (Spatial Frequency Response) or MTF (Modulation Transfer Function) from random scale-invariant (or approximately scale-invariant) test charts, including “Dead Leaves” and “Spilled Coins” charts. It is primarily used to measure the effects of signal processing on image texture. Dead leaves/Spilled Coins charts are of increasing interest because their statistics resemble those of natural […]

Instructions and comments Under development We are updating this page for the latest Skype for Business Video Capture Specification, December 2016. An index of of the Skype/Lync specifications can be found on https://technet.microsoft.com/en-us/office/dn788953 This document contains instructions for using Imatest with the Skype for Business Video Capture Specification, which has two versions: personal solutions (Document Number: H100693) and conferencing devices (Document Number: M1023160), published December 2016. “Skype for Business V3.0” appears on a watermark, and 3.0 is indicated in the Revision History (Section 1). It also contains comments and suggestions for running Imatest. The Skype spec uses only a tiny […]

Instructions and comments We are updating this page for the latest Skype/Lync specification. An index of of the Skype/Lync specifications can be found on  http://technet.microsoft.com/en-us/lync/gg278181.aspx. This document contains instructions for using Imatest with the Skype Hardware Certification Specification — For all Skype Video Devices Version 5.0. It also contains comments and suggestions (some of which we hope might be adopted in a future release of the spec). The Skype spec uses only a tiny fraction of Imatest’s powerful capabilities. To learn more, see Image Quality Factors and SFRplus (which allows many factors to be measured from a single image). In […]